---
type: "fit"
designation: "H9/d9"
hole: "H9"
shaft: "d9"
basis: "hole"
classification: "clearance"
role: "Free running. Good where accuracy is not essential and clearance can be generous."
size_count: 13
standard: "ISO 286-1:2010, ISO 286-2:2010"
verified: "August 1, 2026"
url: https://shopmath.org/fits/h9-d9
---

# H9/d9 Fit — ISO 286 Clearance Fit Limits by Nominal Size

H9/d9 is a clearance fit: at 25 mm nominal it gives 65 to 169 µm clearance. Free running. Good where accuracy is not essential and clearance can be generous. The hole is always larger than the shaft — the parts always assemble with a gap.

- **Designation**: H9/d9
- **Hole tolerance**: H9
- **Shaft tolerance**: d9
- **Basis**: hole basis
- **Classification**: Clearance fit
- **Typical use**: Free running. Good where accuracy is not essential and clearance can be generous.
- **Standard**: ISO 286-1:2010, ISO 286-2:2010

## H9/d9 Hole and Shaft Limits by Nominal Size

Limits in millimetres, clearances in micrometres. A negative clearance is interference — the shaft is larger than the hole and assembly needs force, heat or cold.

| Nominal size | Hole min (mm) | Hole max (mm) | Shaft min (mm) | Shaft max (mm) | Min clearance (µm) | Max clearance (µm) | Result |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 5 mm | 5.000 | 5.030 | 4.940 | 4.970 | 30 | 90 | Clearance |
| 6 mm | 6.000 | 6.030 | 5.940 | 5.970 | 30 | 90 | Clearance |
| 8 mm | 8.000 | 8.036 | 7.924 | 7.960 | 40 | 112 | Clearance |
| 10 mm | 10.000 | 10.036 | 9.924 | 9.960 | 40 | 112 | Clearance |
| 12 mm | 12.000 | 12.043 | 11.907 | 11.950 | 50 | 136 | Clearance |
| 16 mm | 16.000 | 16.043 | 15.907 | 15.950 | 50 | 136 | Clearance |
| 20 mm | 20.000 | 20.052 | 19.883 | 19.935 | 65 | 169 | Clearance |
| 25 mm | 25.000 | 25.052 | 24.883 | 24.935 | 65 | 169 | Clearance |
| 30 mm | 30.000 | 30.052 | 29.883 | 29.935 | 65 | 169 | Clearance |
| 40 mm | 40.000 | 40.062 | 39.858 | 39.920 | 80 | 204 | Clearance |
| 50 mm | 50.000 | 50.062 | 49.858 | 49.920 | 80 | 204 | Clearance |
| 80 mm | 80.000 | 80.074 | 79.826 | 79.900 | 100 | 248 | Clearance |
| 100 mm | 100.000 | 100.087 | 99.793 | 99.880 | 120 | 294 | Clearance |

## Sources and Method for the H9/d9 Fit

### H9/d9 limits

- **Source**: computed from the compiled ISO 286 tables: ISO 286-1 IT grades and ISO 286-2 fundamental deviations, compiled from saucecode/ISO286 (LGPL-2.1) and parkergreene/isofits (MIT), cross-checked cell-for-cell
- **Method**: computed
- **Verified against**: parkergreene/isofits ISO 286-2 limit tables (MIT); ISO 286-1 formula harness — 2067 checks passed

### Assumptions

- Values are the ISO 286-2 tabulated limits, not the ISO 286-1 formula: the formula deviates from the table by up to 13.26% and is carried only as a validation harness.
- Limits are at 20 °C, the ISO 1 reference temperature. Clearance is the assembled gap before any thermal or load effect.
- Dataset scope: COMPILED not computed: the ISO 286-1 formula deviates up to 13.26% from the table and is used only as a harness (warn >5%, fail >15%). EXCLUDED: shaft/hole letters s, t, u and the fits H7/s6, H7/t6, H7/u6 — no free source and an undetermined step constant in the formula.

**Data last verified**: August 1, 2026

## Common Questions About the H9/d9 Fit

### What kind of fit is H9/d9?

H9/d9 is a clearance fit on a hole basis. The hole is always larger than the shaft — the parts always assemble with a gap. Free running. Good where accuracy is not essential and clearance can be generous.

### What is the clearance on a 25 mm H9/d9 fit?

At 25 mm nominal, H9/d9 gives 65 to 169 µm clearance. The hole runs 25.000 to 25.052 mm and the shaft 24.883 to 24.935 mm.

### What hole and shaft tolerances make up H9/d9?

H9/d9 pairs a H9 hole with a d9 shaft. On a hole basis, the hole carries the zero-deviation member and the other side is moved to set the fit.

## Related pages

- Hole tolerance: [H9 limits by size](https://shopmath.org/fits/h9.md)
- Shaft tolerance: [d9 limits by size](https://shopmath.org/fits/d9.md)
- All fits and tolerances: [ISO 286 fit reference](https://shopmath.org/fits.md)
- Full grade table: [ISO 286 tolerance chart](https://shopmath.org/charts/iso-tolerances.md)

---

*Source: [ShopMath](https://shopmath.org/fits/h9-d9) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*